I believe someone suggested the Osprey Atmos 25 as maybe meeting your goals, but thought it might be heavier than you wanted. Per the manufacturer's specs, the Atmos 25 weighs 1 lb 15 oz in size medium. It's a panel loader that falls at the low end of your desired capacity range, at least per manufacturer specs as follows:
Small -- 1400 cu in
Medium -- 1500 cu in
Large -- 1600 cu in
It's described as having extra features like zippered mesh pockets on the hip belt, "air suspension" w/alloy frame, front slash pocket w/zipper, front stretch woven pocket, padded hip belt and shoulder straps, etc. Don't know if it has a sternum strap, but suspect it does since that's pretty common with mass-produced packs these days.
At the moment, Backcountry Gear has the Atmos 25 on sale for $84 ($55 off of $139 retail) at the following link:
I don't have an Atmos 25, but I do have a bigger version that Osprey calls the "Atmos 35" -- a lot heavier than the Atmos 25, but more capacity at 2100 cu in for size medium.
Edit: The photo at Backcounty Gear doesn't show a sternum strap, so maybe it doesn't have one. Have to check specs at the Osprey website.